If you can control a million hosts on the Internet, you can do enormous damage. First, you can launch distributed denial of service (DDOS) attacks so immensely diffuse that mitigating them is well beyond the state-of-the-art for DDOS traceback and protection technologies. Such attacks could readily bring down e-commerce sites, news outlets, command and coordination infrastructure, specific routers, or the root name servers.

Second, you can access any sensitive information present on any of those million machines–passwords, credit card numbers, address books, archived email, patterns of user activity, illicit content–even blindly searching for a “needle in a haystack,” i.e., information that might be on a computer somewhere in the Internet, for which you trawl using a set of content keywords.

Third, not only can you access this information, but you can sow confusion and disruption by corrupting the information, or sending out false or confidential information directly from a user’s desktop.

In short, if you could control a million Internet hosts, the potential damage is truly immense: on a scale where such an attack could play a significant role in warfare between nations or in the service of terrorism.